Require CMake 3.17, remove CMP0051 (microsoft#7287)

Hopefully this works and gets us able to build with CMake 4+.

Author: llvm-beanz

CMakeLists.txt

@@ -17,15 +17,6 @@ if(POLICY CMP0022)
   cmake_policy(SET CMP0022 NEW) # automatic when 2.8.12 is required
 endif()
 
-if (POLICY CMP0051)
-  # CMake 3.1 and higher include generator expressions of the form
-  # $<TARGETLIB:obj> in the SOURCES property.  These need to be
-  # stripped everywhere that access the SOURCES property, so we just
-  # defer to the OLD behavior of not including generator expressions
-  # in the output for now.
-  cmake_policy(SET CMP0051 OLD)
-endif()
-
 if(CMAKE_VERSION VERSION_LESS 3.1.20141117)
   set(cmake_3_2_USES_TERMINAL)
 else()

tools/clang/CMakeLists.txt

@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 2.8.8)
+cmake_minimum_required(VERSION 3.17.2) # HLSL Change - Require CMake 3.17.2.
 
 # FIXME: It may be removed when we use 2.8.12.
 if(CMAKE_VERSION VERSION_LESS 2.8.12)